recovery: Don't report unrecognized option in recovery_main.

recovery_main is only interested in a subset of options. Suppress the
warning for unrecognized options (which are likely intended for
recovery).

Fixes: 141239600
Test: On Pixel 3a, write `--security` flag into /misc and reboot
      recovery. Check that recovery_main no longer reports
      "unrecognized option" warning.
      # echo "recovery\n--security\n" | \
          dd of=/dev/block/by-name/misc conv=notrunc bs=1 seek=64
      # killall -9 recovery
      # cat /tmp/recovery.log
Test: Write `--show_text=foo` instead, and check that recovery reports
      "option `--show_text' doesn't allow an argument".
Change-Id: I1cb3a5ed6db91e41453b8aad00c8608f78ac1fa6

recovery_main.cpp

@@ -351,6 +351,12 @@ int main(int argc, char** argv) {
   std::string locale;
   std::string reason;
 
+  // The code here is only interested in the options that signal the intent to start fastbootd or
+  // recovery. Unrecognized options are likely meant for recovery, which will be processed later in
+  // start_recovery(). Suppress the warnings for such -- even if some flags were indeed invalid, the
+  // code in start_recovery() will capture and report them.
+  opterr = 0;
+
   int arg;
   int option_index;
   while ((arg = getopt_long(args_to_parse.size() - 1, args_to_parse.data(), "", OPTIONS,
@@ -374,6 +380,7 @@ int main(int argc, char** argv) {
     }
   }
   optind = 1;
+  opterr = 1;
 
   if (locale.empty()) {
     if (HasCache()) {